Glueless interlock for folding box panels



April 14, 1953 GLUELESS INTERLOCK FOR FOLDING BOX PANELS Filed April 17, 1948 2 SHEETSSHEET l 26 22 64 Z -fl 30 66 5 f Fig. 2

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A4.- A TTORIVE'YS R. B. MELLER 2,634,899

April 14, 1953 EL 2,634,899

GLUELESS INTERLOCK FOR FOLDING BOX PANELS Filed April 17, 1948 2 SHEETSSHEET 2 INVENTOR.

M MMM a I Arm/ wag Patented Apr. 14, 1953 GLUELESS INTERLOCK FOR FOLDING BOX PANELS Reginald B. Meller, Oakland, Calif., assignor to Bemiss-Jason Company, San Francisco, Calif., a corporation of California Application April 17, 1948, Serial No. 21,637

4 Claims.

This invention relates to improvements in cartons, boxes, trays, and other structures made from blanks of cardboard, paperboard, or other suitable foldable sheet material, hereinafter collectively referred to as boxes or folding boxes.

The invention has particular application to folding boxes of the type which aremaintained ll'l assembled position by glueless interengagement of the panels or flaps which constitute the box or the box blank.

The invention provides, among other features, an improved interlock for the formation, without the use of adhesives, of a rigid box corner, the box corner being so constructed that it resists, in a heretofore unattained degree, forces which would tend to disengage the interlocking portions of the flaps or panels. More particularly, the invention provides an interlock which is extremely resistant to forces acting at an angle against the walls of the box from the inside'of the box and from the outside as well as to forces acting in the planes of the box panels. The result is a gluelessly interlocked box which is extremely resistant to forces exerted on the walls of the box by the box contents, such forces generally acting at right angles with respect to the box walls from the inside, and it is equally resistant to forces acting in the opposite direction, from the outside, the latter type of forces being encountered when the box is tightly overwrapped with a sheet of wrapping material, particularly if the wrapping material has a tendency to shrink.

The invention also provides an improved box corner construction of the aforementioned type permitting insertion of flaps or other portions of a cover or lid between interlocked panels without danger of prying the interlocked panels apart.

While the invention is particularly applicable to the interlocking of panels at a box corner, the invention is not limited to such application but may advantageously be employed wherever it is desired to interlock two panels of a folding box in a rigid manner to form a connection thereb-etween comparable in strength and rigidity to a glued connection but more convenient, quicker, and less expensive to assemble than a glued box.

The interlock provided by the present invention owes its strength in no small measure to a peculiarity of design which results in the board being subjected. to compression rather than tear, compression being the type of force which the board is able to sustain most successfully, whereas tear stress is a far less favorable form of load.

The vari us objects, features and advantages of the invention will appear more fully from a consideration of the detailed description which follows accompanied by drawings showing, for the purpose of illustration, preferred embodiments and applications of this invention.

The invention also consists in certain new and improved details of construction as hereinafter set forth and claimed.

Although the characteristic features of the in-' vention which are believed to be novel will be particularly pointed out in the claims appended hereto, the invention itself, its objects and advantages, and the manner in which it may be carried out may be better understood by referring to the following description taken in connection with the accompanying drawings forming a part of it in which:

Figure 1 is a plan view of a flat box blank embodying the invention, the inside surface of the blank facing the observer;

Figure 2 is a perspective view of a box set up from the blank shown in Figure 1, certain interlocks being shown in half completed condition;

Figure 3 is a fragmentary plan view of a corner portion of a modified blank, the outside surface of the blank facing the observer; and

Figure 4 is a perspective view of a box made from a blank of the type shown in Figure 3.

In the following description and in the claims, various structural details will be identified by specific names for convenience. The names, however, are intended to be as generic in their application as the art will permit. Corresponding reference characters refer to corresponding parts in the several figures of the drawings.

In the drawings accompanying, and forming part of the specification, certain specific disclosure of the invention is made for the purpose of explanation of broader aspects of the invention but it is understood that the details may be modifled in various respects without departure from the principles of the invention and that the invention may be applied to other structures than the ones shown.

The blank A shown in Figure 1 is subdivided by several scored fold lines to provide a bottom or main panel i l to which side wall panels [2 and it are hinged along side fold lines [4 and 55. End" in the art. Flaps 24 and 25 are hingedly connected to the end panel I1 along fold lines 25 and 21 in a similar manner as just described.

The flaps 20, 2|, 24 and 25 are separated from the side panels I2 and I3 by cuts 28, 29, 3B and 3|, respectively, extending to the intersections of the fold lines I4 and I5 with the fold lines I8 and I9. The cuts 28, 29, 34 and 3| include offset portions 32, 33, 34 and 35 which are so shaped as to provide a projecting lock tab 36, 31, 38 and 39 on the side edges of the side panels. The lock tabs 35, 31, 38 and 39 protrude a distance d beyond the side edges of the side panels I2 and I3 formed by the cuts 28, 29, 30 and 3|. The length of the lock tabs is preferably of the order of between two to five times the thickness of the board from which the blank is made. The lock tabs form a part of the glueless interlock as will later become apparent.

The interlocks further comprise internal cuts 4|), 4|, 42 and 43 in the side panels I2 and I3.

The internal cuts 44, 4|, 42 and 43 separate the panels into portions which may be resiliently flexed with respect to each other for the purpose of opening the cuts and inserting into the opened cuts a portion of the flaps 20, 2 I, 24 and 25. The internal cuts 40, 4|, 42 and 43 are preferably of bent outline to form internal tongues 44, 45, 45 and 41 in the panels I2 and I3. The internal cuts '40, 4|, 42 and 43 may extend to the side fold lines I4 and I5, as shown in solid lines, or may be substantially U-shaped as indicated in dotted lines, in which event the portion of the cut shown in solid lines between the broken lines and the side fold lines I4 and I5 would be omitted.

Cut edges 48, 49, 55 and 5| are formed on the flaps 20, 2|, 24 and 25 by external cuts 52, 53, 54 and 55 extending into the body of the flaps from outer edges. The orientation and shape of the cuts 52, 53, 54 and 55 is such that portions of the cut edges formed on the flaps 20, 2|, 24 and 25 will, upon assembly of the blank into box form, move into substantial coincidence with portions of the internal cuts 43, 4|, 42 and 43 so that an edge-to-edge engagement results therebetween as will hereinafter become apparent.

External tongues 56, 51, 58 and 59 are bordered by the external cuts 52, 53, 54 and 55 and an outer edge of the respective flap. These external tongues include tab portions 53, 51, 58' and 59 extending partially beyond the confines of the internal tongues 44, 45, 43 and 41 when the flaps 20, 2|, 24 and 25 are folded face-to-face with the side walls I2 and I3 to form box corners. The purpose of the tab portions will become apparent from a consideration of the assembly procedure of the blank which will be described hereinafter,

Internal cuts 65, BI, 52 and 53 preferably of shallow U shape extend near, or substantially in line with, the fold lines 22, 23, 23 and 21, respectively, to provide slits or apertures adapted to receive the lock tabs 36, 31, 38 and 39. In the illustrated embodiment, the cuts 58, GI, 62 and 53 have substantially the form of a fiat or shallow U and extend into the body of the adjacent end panels I 5 and I1. The cuts form tabs .64, 65, 36 and 51 on the flaps 25, 2|, 24 and 25, respectively, which, upon folding of the last named flaps about their fold lines 22, 23, 25 and 21 automatically open apertures into which the lock tabs 36, 31, 38 and 39 fit. The width of these apertures is preferably made equal to one '4 or two thicknesses of the board so that the respective lock tabs 33, 31, 38 and 33 seat relatively tightly therein without making their insertion difiicult in a high speed assembly operation.

The assembly of the blank A into box form may proceed as follows:

The blank A is first folded along the side fold lines I4 and I5 to bring the side panels I2 and I3 into substantially upright position with respect to the bottom panel II. In this position the stock of the side wall panels I2 and I3 is flexed adjacent the inner cuts 43, 4!, 42 and 43 to deflect the internal tongues 44, 45, 45 and 41 outwardly, thereby opening slits in the side wall panels into which the flaps 23, 2 I, 24 and may thereafter be inserted.

The end panels I5 and I1 are then folded with respect to the bottom panel I! about the end fold lines I8 and I 3, and substantially simultaneously the flaps 25, 2|, 24 and 25 are folded with respect to the end panels I3 and I1 about their respective fold lines 22, 23, 23 and 21. This folding operation automatically causes apertures to open at the internal cuts 30, El, 32 and 63 for insertion of the lock tabs 35, 31, and 33 therein.

The flaps 20, 2|, 24 and 25 are brought into parallel position with the upright side wall panels I2 and I3 before the end panels I5 and I1 are fully folded into upright position with respect to the bottom panel, and the erection of the end panels is then continued while simultaneously the portions 56, 51, 58 and 55 of the flaps are guided into the opened slits 43, 4|, 42 and 43 in the side panels.

This operation brings the cut edges 48, 43, 54 and 5| into substantial coincidence with portions of the internal cuts 40, 4|, 42 and 43 and simultaneously causes the lock tabs 35, 31, 3B and 39 to enter the apertures exposed by the tabs 64, 35, 6B and 61.

The left hand portion of the box illustrated in Figure 2 shows the position which the various portions of the blank assume at the end of the folding operation just described. It will be noted that the assembly of the box corner is complete except for the location of the tab portions 55 and 51' which at this time are on the outside of the side wall panels I2 and I3.

The assembly is completed by pulling the tab portions 56' and 51' to the inside of the box into the position shown by the corresponding tab portions 58 and 59 at the right hand portion of the box as illustrated in Figure 2.

The box corners are now securely interlocked against disengagement. The cut edges 43, 43, and 5| (see Figure 1) engage cut edges formed in the side walls I2 and I5 by the internal cuts 40, 4|, 42 and 43 in edge-to-edge relationship. Forces acting against the end panels I6 and I1 from the inside of the box, for example pressure exerted by the box contents, are resisted by the interlock which sustains compressive stress along the interlocked cut edges. Compressive stress is safely sustained by the board since it lies in the plane of the panels in which direction the board offers its greatest resistance to deformation.

Forces acting against the end panels I3 and I1 in the opposite direction are sustained by pressure of the end panels against the side edges 28, 29, 30 and 3| of the side walls I2 and I3.

Pressure exerted against the side walls I2 and I3 from the inside of the box is safely sustained by the box corners by reason of the reinforce ment afforded by the flaps 28, 2|, '24 and 25 overlying the side walls.

Forces acting on the side walls l2 and 13 from the outside of the box are resisted by the lock tabs 36, 37, 38 and 3% engaging the apertures in the four box corners. The lock tabs 36, 3'1, 38 and 3S prevent folding of the side wall panels I2 and i3 towards the inside of the box. Such folding movement, unless prevented by the corner lock tabs 36, '31, 38 and 39, would tend to disengage the out edges 48, 49, 5G and 5! from the corresponding internal cut edges in the side wall panels !2 and I3.

It is thus seen that the corner tabs 35, 31, 38 and 39 supplement the edge-to-edge interlock formed between the flaps 26, 2|, 24 and 25 and the side walls 52 and [3 to prevent disengagee ment of the edge-to-edge interlock. On the other hand, the edge-to-edge interlock prevents disengagement of the corner tabs 36, 31, 38 and 39 from their respective apertures in the box corner. r

In addition, spaces or pockets are formednear the four corners of the box into which portions of a lid or a cover may be frictionally inserted and securely retained Without danger of prying the side panels and corner flaps apart. This advantage will become apparent from a consideration of the construction and features ofv the box shown in Figure 4. The box shown in Figure 4 is made from a blank B of which, for the reason of simplification, only a corner portion is shown which in the finished box forms the box corner B.

The blank B comprises a bottom panel (38 having a side wall panel 69 connected to it along a side fold line M. An end panel H of equal height as the side panel 59 is hingedly connected to the bottom panel along an end fold line 72. A flap i3 is hingedly connected to the end panel 'li along a fold line M which may be aligned with, or be parallel and slightly offset with respect to, the side fold lines It to compensate for the thickness of the board as set forth in connection with the previously described blank A.

The flap '13 is separated from the side panel 69 by a cut extending to the intersection of the fold lines 12 and 14.

or near the fold line '14. The apertures may be formed by a slit or a U-shaped out 18 extending into the body of the end panel H and forming a protruding portion '19 on the flap '13 which,

upon folding of the flap, automatically opens an aperture adapted to receive the lock tab ll on the side panel 69.

An internal cut 3! outlines a resiliently de-f flectable internal tongue 8! in the side wall panel 69 which, upon deflection with respect to the remainder of the side wall panel, permits insertion of a portion of the flap 13 into the resulting slit or aperture.

A cut edge 32 is formed on the flap 13 by an external cut 83 extending into the body of the flap 13. The cut 83 borders an external tongue 84 having a tip portion 85.

The box shown in Figure 4 is assembled by forming and locking the four box corners in the The cut 15 forms aportion of a side edge 16 of the side wall pan-; els 69. The side edge includes a projecting por-- tion or look tab ll fitting into an aperture at 13 are then folded about their respective fold lines and the flap I3 is partially inserted into the internal cut 8%! after flexing of the internal tongue 8| outwardly with respect to the remainer of the side wall panel 69. The folding operation causes the lock tab 11 to enter the aperture formed by deflection of the tab portion 19. Finally, the tip portion is pulled from the position overlying the side wall panel 69 towards the inside of the box.

The other box corners are assembled in the same manner.

The box comprises a cover 86 hingedly connected to the end wall 87 along a top fold line 88. The cover 86 has depending side flanges of which one is visible at 88. The side flanges are frictionally insertable between the four corner flaps of the box and the respective side panels to maintain the cover in closed position; The cover itself rests on the top edges of the side wall panel, the top edge of the side wall 65 being visible at 89.

The side flanges 88 may be of considerable width and may extend down to the internal cuts- 80. The ends of the side flanges are preferably cut away as shown at 99 and 9! in order to clear the lock tabs Tl.

A depending front flange 92 may be provided as reinforcement of the front edge of the cover adjacent the end wall H.

The depending side flanges of the cover at frictionally engage the side walls and the four corner flaps. The insertion of cover flanges however, does not intefere with, nor in any way detract from, the strength and reliability of the corner locks since the corner locks are constructed to;

resist the prying or wedging action of the de-' pending side flanges bythe corner lock tabs 1'! engaging apertures in the four box corners.

Whereas in the form of box shown in Figure 4 the cover is integral with one end panelof the box, it is evident that the cover maybe entirely. detached from the box and be provided with depending flanges along all four edges of the cover. This is an obvious modification which, because of its simplicity, requires no further explanation.

' The invention thus provides an extremelysecure glueless interlock for box panels suitable for assembly on automatic high-speed machinery of relatively simple construction.

Asthe illustrated forms of boxes show, the invention is equally adaptable to boxes with or without covers. a type of tray which is generally overwrapped with a sheet of transparent wrapping material,

such as cellulose acetate. Overwrapped boxes and trays must sustain considerable force from the outside, caused by the tightness'of the over wrap. The present interlock is admirably suited for such boxes or trays since it will Withstand considerable forces from the outside. The invention is equally applicable to boxes having either. Four pockets.

and described, but may be applied with equal.

benefit to other forms of boxes. Numerous additions, omissions, substitutions and 1 other changes may be made in adapting the invention to specific needs without departure from the spirit and the essence of the present invention;

The box shown in Figure 2 is 7 'What is claimed is:

1. In a box blank of foldable sheet material including, a main panel; a first wall panel hingedly connected to the main panel along a first fold line; a second wall panel hingedly connected to the main panel along a second fold line extending at an angle with respect to the first fold line; and a flap hingedly connected to said first panel along a third fold line extending at an angle with respect to said first fold line, said flap being foldable into face-to-face overlapping position with respect to the second panel, the improvement permitting formation, without the use of adhesives, of said panels and flap into a rigid box corner, the improvement comprising, an internal cut of bent outline in said second panel forming an internal tongue in said second panel adapted to be resiliently flexed with respect to the remainder of said second panel, and an external cut in said flap extending into the body of said flap from an outer edge, said external cut coinciding in interlocking position with a portion of said internal cut in line-to-line, as distinguished from point-to-point coincidence, said external cut forming an external tongue on said fiap resiliently defiectable with respect to the remainder of said flap, said external tongue being bordered by said external cut and by at least one outer edge of said flap, a tab projecting from a side edge of said second panel towards said first panel when the panels are in corner forming position, said side edge being in substantial registry with said third fold line in corner forming position, and an aperture in said first panel along said third fold line adapted to receive said tab, said flap being partially insertable through said internal cut and under said internal tongue, said internal and external cuts being so located with respect to each other and with respect to said tab and aperture that portions of the two cuts are in substantial coincidence, permitting an edge portion formed by one cut to engage a coinciding edge portion formed by the other out in edge-toedge, as distinguished from point-to-point, position when said tab extends into said aperture, said engaged edge portions locking said flap and second panel against parallel shifting with respect to each other, said tab and aperture preventing separation of said flap and second panel from their face-to-face position which would tend to disturb the edge-to-edge engagement, whereby the corner is securely locked to resist forces acting both in the planes of, and at an angle to, said flap and panels both from the inside and from the outside of the corner.

2. In a box blank of foldable sheet material including, a main panel; a first wall panel hingedly connected to the main panel along a first fold line; a second wall panel hingedly connected to the main panel along a second fold line extending at an angle with respect to the first fold line; and a flap hingedly connected to said first panel along a third fold line extending at an angle with respect to said first fold line, said flap being foldable into face-to-face overlapping position with respect to the second panel, the improvement permitting formation, without the use of adhesives, of said panels and fiap into a rigid box corner, the improvement comprising, an internal cut of bent outline in said second panel forming an internal tongue in said second panel adapted to be resiliently flexed with respect to the remainder of said second panel and an external cut in said flap extending into the body of said fiap from an outer edge, said external cut coinciding in interlocking'position with a portion of said internal cut in line-to-line, as distinguished from point-to-point coincidence, said external cut forming an external tongueon said fiap resiliently defiectable with respect to the remainder of said flap, said external tongue being bordered by said external cut and by at least one outer edge of said flap, the side edge of said second panel lying adjacent and in substantial registry with, said third fold line when said panels are in corner forming position and being shaped to provide a protruding tab on said second panel, said third fold line including a U-shaped cut extending into the body of said first panel and forming a tab on said 'fiap, the U-shaped cut producing a self-opening aperture along said third fold line when said flap is folded with respect to said first panel, said aperture being adapted to receive the tab on said second panel, said flap being partially insertable through said internal cut and under said internal tongue, said internal and external cuts being so located with respect to each other and with respect to said tab and aperture that portions of the two cuts are in substantial coincidence, permitting an edge portion formed by one cut to engage a coinciding edge portion formed by the other out in edge-to-edge, as distinguished from point-topoint, position when said tab extends into said aperture, said engaged edge portions locking said fiap and second panel against parallel shifting with respect to each other, said tab and aperture preventing separation of said flap and second panel from their face-to-face position which would tend to disturb the edge-to-edge engagement, whereby the corner is securely locked to resist forces acting both in the planes of, and at an angle to, said flap and panels both from the inside and from the outside of the corner.

3 In a box blank of foldable sheet material including a main panel; a first wall panel hingedly connected to the main panel along a first fold line; a second wall panel hingedly connected to the main panel along a second fold line extending at an angle with respect to the first fold line; and a flap hingedly connected to said first panel along a third fold line extending at an angle with respect to said first fold line, said flap being foldable into face-to-face overlapping position with respect to the second panel, the improvement permitting formation, without the use of adhesives, of said panels and fiap into a rigid box corner, the improvement comprising, an internal cut of bent outline in said second panel forming an internal tongue in said second panel adapted to be resiliently flexed with respect to the remainder of said second panel and an external cut in said flap extending into the body of said flap from an outer edge, said external cut coinciding in interlocking position with a portion of said internal cut in line-to-line, .as distinguished from point-to-point coincidence, said external cut forming an external tongue on said flap resiliently defiectable with respect to the remainder of said flap, said external tongue being bordered by said external cut and by at least one cute edge of said flap, the external tongue being of such outline relatively to the outline of said internal cut that a tab portion of said external tongue extends beyond the confines of said internal tongue of the flap and the second panel are placed face-to-face in the position in which they are to be interlocked, the side edge of said second panel lying adjacent, and in substantial registry with, said third fold line when said panels are in corner forming position and being shaped to provide a protruding tab on said second panel, said third fold line including a U-shaped cut extending into the body of said first panel and forming a tab on said fiap, the u-shaped cut producing a self-opening aperture along said third fold line when said flap is folded with respect to said first panel, said aperture being adapted to receive the tab on said second panel, said fiap being partially insertable through said internal cut and under said internal tongue, said internal and external cuts being so located with respect to each other and with respect to said tab and aperture that portions of the two cuts are in substantial coincidence, permitting an edge portion formed by one cut to engage an edge portion formed by the other cut in edge-to-edge, as distinguished from point-to-point, position when said tab extends into said aperture and said tab portion is forced through said internal cut from a position overlying said second side panel into a position underlying said second side panel, said engaged edge portions locking said fiapand second panel against parallel shifting with respect to each other, said tab and aperture preventing separation of said flap and second panel from their face-to-face position which would tend to disturb the edge-to-edge engagement, whereby the corner is securely locked to resist forces acting both in the planes of, and at an angle to, said fiap and panels both from the inside and from the outside of the corner.

4. In a box blank of foldable sheet material including a main panel; a first wall panel hingedly connected to the main panel along a first fold line; a second wall panel hingedly connected to the main panel along a second fold line extending at an angle with respect to the first fold line; and a flap hingedly connected to said first panel along a third fold line extending at an angle with respect to said first fold line, said fiap being foldable into face-to-face overlapping position with respect to the second panel, the improvement permitting formation, without the use of adhesives, of said panels and flap into a rigid box corner, the improvement comprising, an internal cut in said second panel, and an external cut in said flap extending into the body of said flap from an outer edge, said external cut coinciding in interlocking position with a portion of said internal cut in line-to-line, as distinguished from pointto-point coincidence, said external cut forming an external tongue on said fiap resiliently deflectable with respect to the remainder of said flap, said external tongue being bordered by said external cut and by at least one outer edge of said flap, a tab projecting from a side edge of said second panel towards said first panel when the panels are in corner forming position, said side edge being in substantial registry with said third fold line in corner forming position, and an aperture in said first panel along said third fold line adapted to receive said tab, said flap being partially insertable through said internal out, said internal and external cuts being so located with respect to each other and with respect to said tab and aperture that portions of the two cuts are in substantial coincidence, permitting an edge portion formed by one cut to engage an edge portion formed by the other out in edge-to-edge, as distinguished from point-to-point position when said tab extends into said aperture and when the side edge of said second panel abuts the surface of said first panel in edge-to-surface position, said engaged edge portions locking said flap and second. panel against parallel shifting with respect to each other, said tab and aperture preventing separation of said flap and second panel from their face-to-face position which would tend to disturb the edge-to-edge engagement, whereby the corner is securely locked to resist forces acting both in the planes of, and at an angle to, said flap and panels both from the inside and from the outside of the corner.

REGINALD B. MELLER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 691,458 Ferris Jan. 21, 1902 2,171,051 Stonecypher Aug. 29, 1939 2,228,377 Wendt Jan, 14, 1941 2,274,714 Levkoff Mar. 3, 1942 2,300,491 Ferguson Nov. 3, 1942 2,316,362 Poe Apr. 13, 1943 2,366,419 Meller Jan. 2, 1945 2,475,279 Dunning July 5, 1949 2,488,703 Buttery Nov. 22, 1949 2,528,900 Meller Nov. 7, 1950 2,550,582 Meller Apr. 24, 1951 

